The process of vacuum coating the lens and frame separately

The core of this process is to separate the lens and frame for vacuum coating. The key lies in considering the differences in material (lenses are mostly made of resin/glass, while frames are mostly made of metal/TR90) and functional requirements (lenses focus on optical performance, while frames focus on durability/decorative/aesthetic protection). Different process parameters, coating materials, and procedures are adopted to complete the coating separately and then assemble them. This ensures both optical performance and the durability and aesthetics of the frame. It is a mainstream refined production method in the industry. The overall process is divided into two main lines: the lens vacuum coating process and the frame vacuum coating process. Finally, it is connected with assembly and inspection. The following is the complete industrial standard process, clear and implementable.

Core of the process: Focusing on "optical performance priority", we prioritize ensuring the light transmittance, anti-reflection effect and adhesion of the coating layer. This is consistent with traditional lens coating. The optimization of details and the adaptation for separate production meet the connection requirements.

1. Lens surface treatment (determining the adhesion strength of the film layer, the core step)

   Objective: To thoroughly remove oil stains, dust, static electricity and residual impurities from the lens surface, avoiding issues such as peeling, spots and bubbles after coating, and laying the foundation for the adhesion of the optical film layer.

   Ultrasonic multi-stage cleaning: It undergoes a series of processes including alkaline washing (to remove oil) → normal water washing (to remove alkaline solution) → acid washing (to remove oxidized impurities) → high-purity water washing (to remove acid solution) → overflow rinsing (to remove fine residues). Throughout the process, the purity of the water quality is strictly controlled to avoid water stains remaining.

   Dehydration and drying: After cleaning, place the lenses in a dedicated oven and dry them at a low temperature of 60-80℃. The temperature should be gradually increased and decreased to prevent the lenses from deforming and to ensure that the surface is completely dry and free of any water stains.

   Plasma pre-treatment (activation): After the lenses are dried, they are sent into the pre-vacuum chamber and inert gas is introduced to generate plasma bombardment on the surface of the lenses, increasing the surface energy of the lenses and enhancing the bonding force between the subsequent film layer and the lens base, thus preventing the film layer from peeling off.

2. Lens upper piece and clamping

   After the lenses have undergone pre-treatment, they are precisely installed on the dedicated coating fixture (umbrella frame) according to the requirements of the convex and concave surface orientations (usually with the convex surface facing the evaporation source of the film material). Ensure that the lenses are firmly fixed without any looseness, and at the same time, avoid the fixture blocking the coating area of the lenses. After the clamping is completed, the fixture is sent into the vacuum coating chamber and the chamber door is sealed.

3. Vacuum chamber vacuuming and preheating

   • Rough vacuuming: Start the mechanical pump and draw the air inside the vacuum coating chamber to a low vacuum state (10⁻¹ to 10⁻² Pa), thereby removing most of the air impurities.

   • Complete vacuuming: Start the diffusion pump or molecular pump to further increase the vacuum level to the high vacuum required by the process (10⁻³ to 10⁻⁵ Pa). In this state, air molecules will not interfere with the deposition of atoms/molecules on the film material, ensuring a uniform and dense film layer.

   Lens preheating: After the vacuum degree meets the standard, the lens is subjected to low-temperature preheating (the temperature is adjusted according to the material of the lens, 40-60℃ for resin lenses, 80-100℃ for glass lenses), to ensure the uniform temperature of the lens and reduce the stress of the film layer caused by temperature difference during the subsequent coating process, preventing the film layer from cracking.

4. The lenses undergo formal vacuum coating (multi-layer composite film, the core process)

   The lens coating focuses on "optical functions". It uses vacuum evaporation coating (the mainstream method) or magnetron sputtering coating (for high-end applications). Multiple layers of composite films are deposited in a fixed sequence, and the thickness of each layer is monitored in real time by a crystal control instrument and a light control instrument, with an accuracy of up to the nanometer level.

   1. Step 1: Apply hard coating (optional): If the base of the lens is a resin sheet (with lower hardness), first deposit a layer of organic silicone resin and a hard coating to enhance the surface hardness of the lens, preventing scratches during subsequent use. The thickness of the coating should be controlled between 100 and 200 nanometers.

   2. Step 2: Apply multilayer anti-reflection coating (AR coating): Alternately deposit high refractive index materials (such as TiO₂, ZrO₂) and low refractive index materials (such as SiO₂, MgF₂), with the number of layers typically ranging from 5 to 15. Each layer is about several tens to several hundred nanometers thick. Through the destructive interference of light, the reflection rate of the lens surface is reduced from 8% to 0.2% - 1.5%, while the light transmittance is increased to 98% - 99%, thereby reducing reflections, glare and ghosting.

   3. Step 3: Apply hydrophobic anti-fouling film (AF film): Finally, deposit a layer of fluorinated material to reduce the surface energy of the lens, achieving waterproof, oil-resistant, and fingerprint-resistant effects. This enables the lens stains to be wiped clean immediately and extends the service life of the film layer.

5. Lens cooling, vacuum breakdown and film removal

   • Cooling: After the coating process is completed, stop the heating and allow the lens to cool naturally in the vacuum chamber to room temperature. Avoid rapid cooling which may cause the coating layer to crack or fall off.

   • Breaking the vacuum: Gradually introduce dry nitrogen gas into the vacuum chamber to restore the chamber pressure to normal (breaking the vacuum), to prevent air from rapidly entering and damaging the film layer.

   • Second part: Open the door of the vacuum chamber, remove the coating fixture, carefully take out the lens, and avoid touching the coating surface of the lens to prevent scratches and contamination.

6. Lens inspection (to be kept for future use upon passing)

   The coated lenses are subjected to two rounds of inspections. Once they pass the inspection, they are placed in a dedicated storage area and await assembly with the frames.

   • Visual inspection: Check whether there are any defects such as spots, peeling, chromatic aberration, fingerprints, watermarks, or scratches on the surface of the lens, ensuring that the appearance is intact.

   • Optical inspection: Tests the light transmittance, reflectance and haze of the lenses to ensure compliance with optical standards, and verifies that the anti-reflection and anti-glare effects meet the requirements.

The frame materials are diverse (metal: stainless steel, titanium alloy, copper-nickel alloy; plastic: TR90, PC, etc.). The purpose of coating is to enhance wear resistance, prevent corrosion, and increase aesthetics (such as gold, silver, gun color). The process is significantly different from that of the lens. The core uses magnetron sputtering coating (wear-resistant, strong adhesion).

1. Frame pre-processing (matching the frame material, key anti-slip treatment)

   Objective: Remove the oxide layer, oil stains, stamping residues and fingerprints from the surface of the frame, improve the surface roughness of the frame, enhance the adhesion of the film layer, and prevent the film from peeling off or fading after subsequent coating.

   Polishing and finishing (for metal frames only): Perform meticulous grinding and polishing on the surface of the metal frames to remove surface scratches and oxidation spots, making the frame surface smooth and flat. At the same time, increase the surface roughness to facilitate the adhesion of the film layer.

   Ultrasonic cleaning: Place the frame into the dedicated cleaning solution (for the corresponding material, use alkaline cleaning solution for metals, and neutral cleaning solution for plastics), and perform ultrasonic cleaning to remove oil stains, dust and residual impurities. After cleaning, rinse it thoroughly with pure water.

   Dehydration and drying: Place the cleaned spectacle frames in an oven and dry them at a low temperature (40-50℃). Ensure that there is no moisture or residue on the surface. For plastic spectacle frames, the temperature needs to be controlled to prevent deformation.

   Ion bombardment (optional, to enhance adhesion): After the frame is dried, it is sent into the vacuum chamber for ion bombardment treatment. This process removes the minute impurities and oxide layers remaining on the surface, further enhancing the surface energy and making the film layer bond more firmly to the frame.

2. Lens upper piece and clamping

   Fix the pre-treated spectacle frames on the dedicated fixture (customized according to the shape of the frames to avoid covering the coating area), ensuring that the frames are not loose or deformed. During clamping, avoid touching the surface of the frames to prevent scratching. After clamping is completed, send the fixture into the magnetron sputtering vacuum coating chamber and close the chamber door to seal it.

3. Vacuum chamber vacuuming and atmosphere adjustment

   • Vacuum pumping: First, start the mechanical pump for rough pumping, then start the molecular pump for fine pumping. Raise the vacuum level inside the vacuum coating chamber to 10⁻³ to 10⁻⁴ Pa to ensure that there are no air impurities interfering with the film deposition.

   • Atmosphere adjustment: A small amount of inert gas (mainly argon) is introduced into the vacuum chamber to create a plasma environment, which provides conditions for subsequent magnetron sputtering and protects the surface of the spectacle frame from oxidation.

4. Frame is subjected to formal vacuum coating (with emphasis on wear resistance and decoration)

   The coating of the frame is mainly carried out by the magnetron sputtering process. According to the requirements, different coating materials are selected, and it is divided into three layers: base coating, functional coating, and decorative coating. This ensures durability, corrosion resistance, and aesthetic appeal.

   1. Step 1: Apply base coating (core anti-corrosion): Deposit a layer of metal base coating (such as chromium, titanium, or nickel), with a thickness of 50-100 nanometers. The main function is to enhance the adhesion between the subsequent coating layer and the frame, and at the same time prevent the metal frame from oxidizing and rusting (this step can be omitted for plastic frames).

   2. Step 2: Apply protective coating (for wear resistance): Deposit a layer of wear-resistant functional coating (such as DLC type ultra-hard coating or titanium nitride), with a thickness of 100-200 nanometers. This will enhance the hardness of the frame surface, prevent scratches and wear during use, and extend the service life.

   3. Step 3: Apply decorative coating (optional, for enhancing appearance): Depose the decorative coating material (such as titanium gold, rose gold, gun color, black) according to requirements. The thickness should be 50-100 nanometers. Ensure uniform color and no color difference, enhancing the appearance texture of the frame. The decorative coating must also have good wear resistance to prevent easy color fading.

5. Frame cooling, vacuum breakdown and film lowering

   • Cooling: After the coating process is completed, stop the sputtering and allow the frame to cool naturally in the vacuum chamber to room temperature. Avoid rapid cooling which may cause the coating layer to crack or fade.

   • Remove vacuum: Gradually introduce dry nitrogen gas to restore the normal pressure inside the chamber, to prevent air from rapidly entering and damaging the membrane layer.

   • Second part: Open the door of the vacuum chamber, remove the fixture, carefully take off the spectacle frame, avoid touching the coated surface, and place it in a dedicated container for later use.

6. Frame inspection (to be kept for future use upon passing)

   Conduct a comprehensive inspection of the coated frame, and if it is qualified, send it to the assembly area for assembly in conjunction with the lens.

   • Appearance inspection: Check whether the surface color of the frame is uniform, whether there is color difference, peeling, scratches, blemishes, fingerprints, and whether the frame is deformed.

   • Performance test: Test the wear resistance of the coating on the frame (wipe with a special tool, no color fading or scratches), adhesion (stick with tape, no peeling), and corrosion resistance for metal frames (simple salt spray test, no oxidation).

• Storage and isolation: The coated lenses and frames should be stored separately. The lenses should be placed in a dedicated dust-proof bag, and the frames should be placed in a dedicated packaging box to prevent them from rubbing against each other and scratching the coated surface.

• Assembly protection: When assembling the glasses, the operator should wear dust-free gloves to prevent fingerprints and oil from contaminating the coating surfaces of the lenses and frames; when installing the lenses, avoid applying excessive force to prevent damage to the edge of the lens coating.

• Overall inspection: After the assembly is completed, a final inspection is conducted on the entire pair of glasses to ensure that the lenses are transparently light-transmitting, without abnormal reflections, that the frame color is uniform and there is no peeling off, and that the overall wearing is comfortable and free of defects.